Photovoltaic cell, method for assembling plurality of cells and assembly of a plurality of photovoltaic cells

ABSTRACT

The photovoltaic cell has a block that includes at least one semiconductor substrate in which is formed at least one photovoltaic junction that is connected to a first electrical contact element of a first pole and to a second electrical contact element of a second pole. The cell includes a first transparent cover that is placed on a first surface of the block and defines with the block of the cell a first recess groove of a first electrically conductive wire element.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a photovoltaic cell provided with a blockincluding at least one semiconductor substrate in which is formed atleast one photovoltaic junction connected to a first electrical contactelement with a first pole and to a second electrical contact elementwith a second pole.

STATE OF THE ART

Current photovoltaic panels comprise lines of solar cells electricallyconnected in series.

FIG. 1 represents three solar cells 1 a, 1 b, 1 c connected in series. Acell comprises a semiconductor substrate 2 a in which at least onejunction PN is formed. A cell has usually the form of a square with aside of approximately 16 cm. The electrical contact elements arearranged on both sides of the substrate 2 a. In FIG. 1, a firstelectrical contact element 3 with a negative pole is arranged on theface of each cell 1 a, 1 b, 1 c designed to be oriented towards the sun.In order to increase the yield of a solar cell while letting photonsthrough, the first electrical contact element 3 is constituted by anelectrode provided on both sides of its longitudinal axis of combs. Asecond electrical contact element with a positive pole is formed by ametal layer 4 covering the back face of the cell. A series of solarcells is made by welding electrically conducting bands 5 a, 5 b, 5 cbetween two adjacent cells. Thus, a first cell 1 a is linked to a secondcell 1 b by a band 5 b welded at one end to the metal layer 4 of thesecond cell 1 b and at another end to the first electrical contactelement 3 of the first cell 1 a. The second cell 1 b is connected to athird cell 1 c by a band 5 b welded at one end to the metal layer 4 ofthe third cell 1 c and at another end to the first electrical contactelement 3 of the second cell 1 b. The step which consists in linkingseveral cells together becomes increasingly difficult to carry out sincecurrent technologies tend to make cells thinner in order to savematerials, in particular when they are made on silicon substrates.

Indeed, the rigid solar cells are to date mainly produced fromincreasingly fine silicon plates. Materials and manufacturing processesare the subject of research programs in order to reduce the productioncosts by diminishing the quantity of silicon per wafer. For that, thethickness of the silicon wafers has been first of all reduced from 300μm to 200 μm, and it is now thought to reach a thickness of 180 μm, even150 μm. As result of this reduction in thickness, the cells has becomemore and more fragile and their handling difficult.

Moreover, once the cells are connected together to form a panel, thepanel is encapsulated within a massive framework in order to protect thewhole. The final panel is often relatively thick.

In addition, making flexible solar panels requires in a general way theuse of “flexible” semiconductor materials whose performance is lowerthan that of “rigid” semiconductor materials such as single-crystalsilicon.

OBJECT OF THE INVENTION

The object of the invention consists in making a photovoltaic cell easyto conceive and to handle, while allowing to make flexible assemblieswith low thicknesses.

This object is reached in that the cell comprises a first transparentcover arranged on a first face of the block and delimiting with saidcell block a first groove for housing a first electrically conductingwire element.

According to one embodiment the cell comprises a second cover arrangedon a second face of the block, opposite the first face of the block, anddelimiting with the cell block a second groove for housing a secondelectrically conducting wire element.

According to an alternative, the second cover and/or first cover areplaced directly on the semiconductor substrate.

According to another embodiment, at least one of the electrical contactelements connected to the photovoltaic junction comprises a wire elementembedded in a groove.

-   -   According to another embodiment, at least one of the electrical        contact elements comprises a plurality of conducting arms        arranged on a face of the semiconductor substrate, said arms        being designed to be in contact with or to be linked to a wire        element.

According to another embodiment, as the second cover is transparent, theblock comprises two semiconductor substrates including photovoltaicjunctions separated by a metal layer, the cell comprising a thirdlongitudinal groove for housing a third electrically conducting wireelement designed to be connected to said metal layer.

According to another embodiment, the block comprises two semiconductorsubstrates including photovoltaic junctions separated by a dielectric,the cell comprising third and fourth grooves respectively formed on aside face at the interface between the dielectric layer and theassociated semiconductor substrates.

Another object of the invention consists of an assembly of photovoltaiccells including several photovoltaic cells linked to one another byseveral wire elements, each wire element being embedded in the groovesof at least two photovoltaic cells.

Another object of the invention consists of a method for assembling aplurality of photovoltaic cells, each cell comprising first and secondgrooves formed on the same side face, the method comprises the followingsuccessive steps:

-   -   positioning cells in the form of at least one line so as to form        a first and a second lines of grooves, the first groove of one        cell being aligned with the second groove of the adjacent cell,    -   wiring each line of cells, a first electrically conducting wire        being inserted into each groove of the first line of grooves,        and a second electrically conducting wire being inserted into        each groove of the second line of grooves,    -   alternatively cutting first and second wires between two        adjacent cells,    -   reversing every second photovoltaic cell in order to orient all        the first covers of the photovoltaic cells towards the same        side.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics will more clearly arise from thefollowing description of particular embodiments of the invention givenas nonrestrictive examples and represented in the annexed drawings inwhich:

FIG. 1 illustrates three solar cells connected according to a knowntechnique of the prior art.

FIG. 2 illustrates a first embodiment of a photovoltaic cell accordingto the invention.

FIG. 3 illustrates a top view of the cell in FIG. 2.

FIG. 4 illustrates an alternative of the first embodiment.

FIG. 5 illustrates a second embodiment of a cell according to theinvention.

FIG. 6 illustrates an alternative of the second embodiment.

FIG. 7 illustrates a third embodiment of a photovoltaic cell providedwith three grooves.

FIG. 8 illustrates a fourth embodiment of a photovoltaic cell accordingto the invention.

FIG. 9 illustrates a fifth embodiment of a photovoltaic cell accordingto the invention.

FIGS. 10 to 16 illustrate a method for assembling a plurality ofphotovoltaic cells in the form of a line.

FIG. 17 illustrates an implementation alternative of the method forassembling a plurality of photovoltaic cells.

FIG. 18 illustrates a plurality of photovoltaic cells arranged in theform of matrix.

FIGS. 19 to 22 illustrate an example of a method for manufacturingphotovoltaic cells.

DESCRIPTION OF PREFERENTIAL EMBODIMENTS

In the embodiments illustrated in FIGS. 2 to 9, a photovoltaic cell isprovided with a block 2 including at least one semiconductor substrate 2a in which at least one photovoltaic junction is formed. A photovoltaicjunction can consist of a junction PN. Each photovoltaic junction isconnected to a first electrical contact element with a first pole and toa second electrical contact element with a second pole. The photovoltaiccell comprises a first transparent cover 6 a arranged on a first face ofthe block 2 and delimiting with the block 2 a first groove 7 a forhousing a first electrically conducting wire element.

Preferably, the first groove 7 a is a longitudinal groove for housingthe first wire element on a side face 8 of the cell.

The first and second poles correspond, for example, to an anode and acathode. The first and second electrical contact elements allow thecollection of the charges, electrons and holes of electrons, generatedin the semiconductor substrate.

The cover 6 a preferably comprises a shoulder at one of its longitudinaledges. The block 2 preferably has dimensions appreciably equal to thedimensions of the first cover 6 a. Thus, when the first cover 6 a is inposition on the block 2 as illustrated in FIG. 2, and the face of thefirst cover 6 a with a notch forming the shoulder is oriented towardsthe first face of the block 2, the first longitudinal groove 7 a isnaturally delimited. The first groove 7 a is then made of a bottom 9 alinked to two side walls 9 b, 9 c. The side wall 9 b and the bottom 9 aare delimited by the shoulder of the first cover 6 a and the other sidewall 9 c is delimited by a free portion of the first face of the block2.

The first wire element is preferably embedded longitudinally in thefirst groove 7 a. By longitudinal embedding it is understood that theaxis of the wire element is substantially parallel to the longitudinalaxis of the groove in which it is embedded.

According to a first particular embodiment illustrated in FIGS. 2 and 3,the block 2 is made up of only one semiconductor substrate and the firstcover 6 a can be placed directly on the semiconductor substrate. Thefirst electrical contact element can comprise a plurality of conductingarms 10 arranged on a first face of the substrate. The second electricalcontact element can comprise a metal layer 4 formed on a second face ofthe semiconductor substrate opposite the first face of the substrate. Inother words, the metal layer 4 covers the semiconductor substrate.Preferably, the arms 10 are substantially perpendicular to alongitudinal axis of the first groove 7 a, and are arranged between thefirst cover 6 a and the first face of the substrate. Preferably, the ams are electrically connected to the groove by means of an electricallyconducting connection arm (not represented) covering at least a part ofthe side wall 9 c of the first groove 7 a formed by the portion ofsubstrate. The arms 10 are preferably placed at a distance to oneanother so as to optimize the active surface of the cell. In otherwords, at least one of the electrical contact elements comprises aplurality of conducting arms 10 arranged on a face of the semiconductorsubstrate, said arms 10 being designed to be in contact with or to belinked to a wire element.

The arms 10 and the connection arm can be made out of a metal or anotherconducting material deposited, or formed, on the substrate 2.

According to an alternative, the connection arm is not necessary, thearms 10 cover a part of the side wall 9 c of the first groove 7 a formedby the free portion of the semiconductor substrate. The arms 10 areelectrically connected together when the first electrically conductingwire element is embedded longitudinally in the first groove 7 a. Whensaid first wire element is in electrical contact with the substrate, forexample when the wire is made up of only one conducting material, saidfirst wire element then constitutes a part of the first of contactelement. In other words, at least one of the electrical contact elementsconnected to the photovoltaic junction comprises a wire element embeddedin a groove.

According to another alternative, if the cell, and more particularly thesemiconductor substrate, has dimensions lower than a minimal distancemaking it possible to attract a great number of electrons or holes ofelectrons generated by the absorption of photons, the arms 10 are thennot essential. The first electrically conducting wire element, once itis longitudinally embedded in the first groove 7 a, can alone act as thefirst electrical contact element.

An assembly of such cells in series with electrically conducting wireelements comprises, between each cell, a electrically wire elementconnecting the first groove 7 a of a first cell to the metal layer 4 ofa second cell.

According to an alternative of the first embodiment illustrated in FIG.4, the free face of the metal layer 4 is covered by a second cover 6 bin the center of which a second groove 7 b is made, preferably with alongitudinal axis substantially parallel to the longitudinal axis of thefirst groove 7 a. This second groove 7 b makes it possible to facilitatethe assembly of a series of cells by delimiting a groove in which asecond electrically conducting wire element can be inserted, for exampleby longitudinal embedding. As in FIG. 4, the cell can comprise a secondcover 6 b arranged on a second face of the block 2, opposite the firstface of the block 2, and delimiting with the block 2 of the cell asecond groove 7 b for housing a second electrically conducting wireelement.

Of course, if the cell has small dimensions, the metal layer can beremoved and the second electrical contact element is then formed by thesecond electrically conducting wire element in contact with thesubstrate. In this case, only the second cover 6 b remains to protectthe semiconductor substrate.

According to another alternative not represented, the metal layer 4 issufficiently thick to make the second groove 7 b in the free face ofthis metal layer 4. The cover 6 b is then not essential.

According to a second embodiment illustrated in FIG. 5 and in which theblock 2 comprises a single semiconductor substrate provided with aphotovoltaic junction, the cell comprises a second cover 6 b arranged ona second face of the semiconductor substrate, opposite the first face ofsaid substrate, and delimiting with the substrate, preferably in a sideface 8 of the cell, a second longitudinal groove 7 b for housing asecond electrically conducting wire element. This second groove 7 b ispreferably substantially parallel to the first groove 7 a, i.e. it has alongitudinal axis parallel to the longitudinal axis of the first groove7 a. The second groove 7 b is preferably located in the same side face 8as the first groove 7 a to facilitate the method of assembling aplurality of cells, as it is described hereafter in relation to FIGS. 12and 13. The first and second electrical contact elements can be totallyor partly composed of at least the first and second wire elementsrespectively longitudinally embedded in the first 7 a and second 7 bgrooves.

In FIG. 5, a metal layer 4 is preferably interposed between thesemiconductor substrate and the second cover 6 b in order to totally orpartly form the second electrical contact element, said metal layer 4being in electrical contact with the second wire element after itsembedding into the second groove 7 b. As described previously, theembodiment in FIG. 5 can also integrate arms arranged between the firstcover 6 a and the semiconductor substrate.

According to an alternative of the second embodiment illustrated in FIG.6, the second cover 6 b is transparent too. This makes it possible tocollect charges produced by photons interacting in the semiconductorwhile going through the first cover 6 a and/or the second cover 6 b.Consequently the metal layer 4 can be replaced by arms, similar to thepreviously-described arms 10, and interposed between the second cover 6b and the semiconductor substrate. The conducting arms are, for example,perpendicular to a longitudinal axis of the second groove 7 b. Theconducting arms can be electrically connected together by a conductingconnection arm. This connection arm is preferably placed under thefuture embedded wire element, i.e. on the side wall of the second groove7 b formed by the portion of substrate, in order not to increase theobstruction to photons induced by the presence of the conducting arms onthe surface of the substrate and the presence of the future wireelement.

As indicated previously, if the cell has small dimensions, the arms arenot essential. The first and second electrically conducting wireelements, respectively longitudinally embedded in the first and secondgrooves 7 a, 7 b, can form alone the first and second electrical contactelements. Consequently, the first 6 a and/or the second 6 b covers canbe placed directly on the semiconductor substrate.

According to a third embodiment illustrated in FIG. 7, the cell includesa central block 2 sandwiched between two covers 6 a, 6 b. Moreprecisely, the cell includes a stack composed of a first transparentcover 6 a, of a first semiconductor substrate 2 a provided with a firstphotovoltaic junction, of a metal layer 4, of a second semiconductorsubstrate 2 b provided with a second photovoltaic junction, and of asecond transparent cover 6 b. The first cover 6 a and the semiconductorsubstrate 2 a delimit on a side face 8 of the cell a first longitudinalgroove 7 a for housing an electrically conducting wire element. Thesecond cover 6 b and the semiconductor substrate 2 b delimit on a sideface 8 of the cell a second longitudinal groove 7 b for housing a secondelectrically conducting wire element. Moreover, the first 2 a and second2 b semiconductor substrates are, in this example, larger than the metallayer 4 on the side of the side face 8. Thus, the metal layer 4 and thefirst and second substrates 2 a, 2 b delimit on the side face 8 of thecell a third longitudinal groove 7 c for housing a third electricallyconducting wire element designed to be linked to the metal layer 4. Inother words, as the second cover 6 b is transparent, the block 2comprises two semiconductor substrates 2 a, 2 b including photovoltaicjunctions separated by a metal layer 4, the cell moreover comprising athird longitudinal groove 7 c for housing a third electricallyconducting wire element designed to be linked to said metal layer 4. Thethird groove 7 c comprises a longitudinal axis, preferably substantiallyparallel to the longitudinal axis of the first groove 7 a. Preferably,the three grooves 7 a, 7 b, 7 c are formed in the same side face 8 ofthe cell to facilitate its assembly with other cells. Such a cell canreceive photons from the two main faces of the cell.

Preferably, conducting arms similar to those indicated for theembodiment illustrated in FIG. 6 are respectively interposed between thefirst cover 6 a and the substrate 2 a, and between the second cover 6 band the substrate 2 b. Of course, if the cell has small dimensions, thearms are not essential.

In this embodiment (FIG. 7), the cell includes two photovoltaicjunctions formed respectively in the semiconductor substrates 2 a and 2b. Each photovoltaic junction is connected to a first and a secondelectrical contact element. The third wire element, placed in the thirdgroove 7 c, will be linked to a contact element of the upperphotovoltaic junction (in the substrate 2 b) and to a contact element ofthe lower photovoltaic junction (in the substrate 2 a). According to theconnections that will be carried out via the first, second and thirdwire elements embedded in the grooves of the cell, the two photovoltaicjunctions can finally be mounted in series or in parallel.

According to an alternative, if the cell has small dimensions, the metallayer 4 can be replaced by a dielectric. The third groove 7 c is thendelimited by the dielectric and two opposite portions of thesemiconductor substrates 2 a and 2 b. The wire element inserted in thethird groove 7 c forms a electrical contact element common to bothphotovoltaic junctions.

An assembly example for several cells such as those in FIG. 7 isdescribed hereafter. It is used a Y-shaped electrically conducting wireelement with two secondary arms connected to a main arm. The secondaryarms are respectively inserted into the first and second grooves 7 a, 7b of a cell. The main arm of the Y-shaped wire element will be embeddedin the third groove 7 c of an adjacent cell. The two photovoltaicjunctions 2 a, 2 b of each cell are then mounted in parallel and thecell is equivalent to a single junction connected to common first andsecond poles.

In such an assembly, the Y-shaped wire element can be composed of twowires meeting at the third groove to form the main arm of the Y.

According to a fourth embodiment illustrated in FIG. 8, the cell alwayscomprises first and second transparent covers 6 a, 6 b, each of themdelimiting with a central block 2 a longitudinal groove for housing awire element 7 a, 7 b. The block 2 comprises two semiconductorsubstrates 2 a, 2 b including photovoltaic junctions, separated by adielectric 2 c. A third longitudinal groove 7 c and a fourthlongitudinal groove 7 d, preferably substantially parallel to the firstgroove 7 a, are formed respectively at the interfaces between thedielectric layer 2 c and the associated semiconductor substrates 2 a, 2b. Preferably, the third 7 c and fourth 7 d grooves are made in the sameside face of the cell as the first and second grooves 7 a, 7 b.

Moreover, the block 2 can comprise the metal layers 4 a, 4 b interposedbetween the semiconductor substrates 2 a, 2 b and the dielectric 2 c onboth sides of the dielectric 2 c. The metal layers 4 a, 4 b enable tooptimize the yield of a cell if its dimensions do not allow the wireelements to collect all the charges generated in the semiconductorsubstrates.

According to an alternative applicable to all the embodiments, eachcover 6 a, 6 b can form a concentrator of the solar radiations towardsthe associated semiconductor substrate. This makes it possible toimprove the yield of each photovoltaic cell. As a particular example, atransparent cover can comprise a plurality of lenses making the photonsconverge into the associated semiconductor substrate.

In a general way, the yield of the cell falls when the semiconductorheats. Thus, at least one of the covers can form a heat sink, whileusing, for example, a comb-shaped cover made out of a thermo-conductingmaterial. For example, a concentrating transparent cover and a heat sinkcover can be envisaged.

According to a fifth embodiment illustrated in FIG. 9, the cell is ofthe type of those illustrated in FIGS. 5 and 6, i.e. it comprises on afirst side face 8 a first and second grooves 7 a, 7 b. The cell in FIG.9 moreover comprises on a second face side 8 b, opposite and preferablyparallel to the first side face 8 a, longitudinal third and fourthgrooves 7 c, 7 d for housing a wire element. These grooves 7 c, 7 d arepreferably also delimited by a shoulder in the associated cover and bythe semiconductor substrate. The assembly of two cells in series can becarried out by a first wire element inserted both in the first groove 7a of a first cell and in the second groove 7 b of a second cell. In thesame way a second wire element is inserted both in the third groove 7 cof the first cell and in the fourth groove 7 d of the second cell. Thismakes it possible to obtain a series of cells maintained on two oppositeside faces thus improving the solidity of the assembly. Moreover, if oneof the wire elements breaks, the second will still be able to ensure thecontinuity in the series of cells. According to the dimensions of thecells, these wire elements can be sufficient for forming the first andsecond electrical contact elements. If not, it is possible to form armsbetween each cover and the substrate as previously described. Of course,the person skilled in the art can adapt this principle to theembodiments in FIGS. 7 and 8.

Thanks to such cells, the semiconductor substrate is protected from theexternal environment by the two covers 6 a, 6 b or by the firsttransparent cover 6 a and the metal layer 4 formed under the cell. Thus,contrary to the methods for assembling traditional photovoltaic cells,it is not necessary to assemble the various photovoltaic cells accordingto the invention in a specific environment with few dust (in order toavoid the contamination of the semiconductor substrates).

Moreover, the covers 6 a, 6 b give a certain rigidity to the whole, andallow an easier handling of the cells during the assembly. As anexample, the thickness of the semiconductor substrate is about 200 μmand each cover has a thickness of 200 μm.

A plurality of cells as described can be assembled in order to form aflexible photovoltaic panel, being able to be incorporated into afabric. The flexibility of the panel is made possible by the use of aplurality of cells of small size, preferably with a side lower than 5mm.

In a general way, an assembly of photovoltaic cells comprises severalphotovoltaic cells connected to one another by several wire elements,each wire element being embedded in the grooves of at least twophotovoltaic cells.

Moreover, the assembling method according to the present invention makesit possible to make photovoltaic panels of very small dimensionscomprising some cells of small size.

In the particular case when the cells are able to collect the solarradiations on both sides (by two transparent caps), an assembly of suchcells comprises a first face designed to be oriented towards the sun.Reflecting means can be arranged on the second face of the assembly.Indeed, when the first face is oriented towards the solar radiations, apart of the solar radiations goes between the cells and is not absorbedvia the first face. The reflecting means then make it possible tocollect these radiations and to give them back towards the transparentcovers of the second face. Such means can be formed, for example, by analuminum or silver foil, patterned or not.

According to a particular embodiment example of a assembly using cellscomprising in the same side face two longitudinal grooves for housingwire elements, illustrated in FIGS. 10 and 11, the cells are first ofall positioned in the form of at least one line so as to form first andsecond rows of grooves. The cells are arranged so that the first groove7 a of a cell is aligned with the second groove 7 b of the adjacentcell. As illustrated in FIG. 11, the cells have preferably the same sizeand form.

The particular example illustrates four cells A, B, C, D, each of themcomprising two longitudinal grooves 7 a, 7 b on a side face of thephotovoltaic cell. In FIG. 10, the cell A and the cell C have theirfirst transparent cover 6 a oriented towards the top, while the cells Band D have their first transparent cover 6 a directed downwards. This iswhy the first row of grooves (top row in FIG. 10) is composed (from leftto right) of the first groove 7 a of the photovoltaic cell A, the secondgroove 7 b of the photovoltaic cell B, of the first groove 7 a of thephotovoltaic cell C and of the second groove 7 b of the photovoltaiccell D. In the same way, the second row of grooves (bottom row in FIG.10) is composed (from left to right) of the second groove 7 b of thephotovoltaic cell A, of the first groove 7 a of the photovoltaic cell B,of the second groove 7 b of the photovoltaic cell C and of the firstgroove 7 a of the photovoltaic cell D.

After positioning the cells suitably, these cells are wired on each lineas illustrated in FIGS. 12 and 13. A first electrically conducting wire11 a is inserted in each groove of the first row of grooves (top groovesin FIG. 12), and a second electrically conducting wire 11 b is insertedin each groove of the second row of grooves (bottom grooves in FIG. 12).Thus, in the particular example, the first wire 11 a extends in thefirst groove 7 a of the cell A, the second groove 7 b of the cell B, thefirst groove 7 a of the cell C and the second groove 7 b of the cell Dwhereas the second wire 11 b extends in the second groove 7 b of thecell A, the first groove 7 a of the cell B, the second groove 7 b of thecell C and the first groove 7 a of the cell D. Then, the first andsecond wires 11 a and 11 b are alternatively sectioned between twoadjacent cells (FIG. 14) in order to form the first and second wireelements of each cell. In fact, the first wire element of a cell formsalso the second wire element of the adjacent cell. The first and secondwires 11 a, 11 b must be good conductors with low ohmic losses. As anexample, it will be used wires out of copper or containing an alloy ofsilver and copper.

During sectioning, as the particular example in FIG. 14 illustrates it,the first wire 11 a in the grooves in the upper part in FIG. 12 issectioned between the cells A and B, and between the cells C and D. Thesecond wire 11 b in the low grooves is sectioned between the cells B andC. Finally, two adjacent cells are linked by a single segment of wireforming both the first wire element of a cell and the second wireelement of the adjacent cell. The cell A is connected to the cell B by asegment of the second wire 11 b, the cell B being connected to the cellC by a segment of the first wire 11 a and the cell C being connected tothe cell D by a segment of the second wire 11 b.

Preferably, in order to avoid any short-circuit, when a wire 11 a, 11 bis sectioned between two adjacent cells, it is cut at the groove of saidtwo adjacent cells as in FIG. 14.

After suitably sectioning the first and second wires 11 a, 11 b, everysecond photovoltaic cell is turned over (FIG. 15) in order to orient allthe first covers of the cells on the same side. By turning over it isunderstood that the cell carries out a rotation of 180° relative to itsinitial position along an axis parallel to the first and second wires 11a and 11 b.

FIGS. 15 and 16 illustrate respectively in a side view and a top viewthe configuration of the cells after the turning-over step. The positionof the cells A and C remains unchanged whereas the position of the cellsB and D is reversed. In this configuration, the first covers 6 a of eachcell are oriented upwards and all the grooves 7 a are then located inthe upper part of the line of cells.

According to an alternative, after the photovoltaic cells are turnedover, each line of cells is then stretched to allow the cells of thesame line to be alternatively arranged on both sides of a central axisof the line of cells, as illustrated in FIG. 17.

This methods enables to connect in series photovoltaic cells asdescribed in a simplified way and to obtain a flexible assembly.

The yield of a plurality of lines of photovoltaic cells in series can beimproved by making an assembly in the form of a matrix. Thus, in analternative, the assembling method comprises the making of a pluralityof identical lines of cells. After the turning-over step, and preferablyafter the stretching step, the lines are arranged so as to form a matrixof lines and columns of cells as in FIG. 18. Two columns of adjacentcells are separated by an interval. Then, at each interval, a third wireelectrically connects the conducting wire elements connecting twoadjacent cells of each line of the matrix at this interval.

According to the particular example in FIG. 18, the matrix comprisesfour lines 12 a, 12 b, 12 c, 12 d arranged so as to form four columns ofcells 13 a, 13 b, 13 c, 13 d. The first and second columns 13 a, 13 b,the second and third columns 13 b, 13 c, and the third and fourthcolumns 13 c, 13 d are each separated from one another by a respectiveinterval Int1, lnt2, lnt3. At each interval, a third wire 14 a, 14 b, 14c, is arranged and electrically connected to each line of cells. Thiselectric connection can be carried out by welding the third wire to eachsegment of wire element linking two adjacent cells of the same line inthis interval. Thus, in FIG. 18, each line corresponding to a line inFIG. 17, the wire 14 a links in the interval Int1 the wire elements ofeach line together, the wire 14 b links in the interval lnt2 the wireelements 11 a of each line together and the wire 14 c connects in theinterval lnt3 the wire elements 11 b of each line together.

In order to limit the losses of performance when one or several cellsare shaded, it is possible to use bypass diodes on one or more solarcells. In practice, a photovoltaic cell can be regarded as a currentgenerator in parallel with a diode (formed by the photovoltaic junctionof the solar cell), the intensity of the current depending on theincidental illumination of the cell. When the cell is shaded, thecurrent is very low even zero. On a line of photovoltaic cells inseries, if a cell is shaded, the current generated by the line of cellscannot circulate in it and the production of current becomes very low orzero. A bypass diode makes it possible to form a derivation of thecurrent in order to limit the impacts of a cell which would be shaded orwhich could have a defect of design limiting its yield. Several modes ofinsertion of bypass diodes on an assembly of photovoltaic cellsaccording to the present invention can be considered by the man skilledin the art.

In the case, for example, of an assembly such as that illustrated inFIG. 18, it is possible to add an additional line of bypass diodes, sothat each additional diode of this additional line is connected inparallel to all the photovoltaic cells of a column. More precisely, theanode and the cathode of each additional diode are respectivelyconnected to the cathodes and the anodes of the diodes formed by thephotovoltaic junctions of the photovoltaic cells of a column. Each ofsuch additional diodes can be made in the form of a microchip having twogrooves provided with conducting studs respectively connected to theanode and the cathode of a diode of the respective microchip. Theadditional diodes can then be connected to one another and to thephotovoltaic cells of the assembly according to a method for assemblingidentical to that described above. Preferably, the dimensions of suchmicrochips are substantially the same as those of the photovoltaic cellsof the assembly in order to guarantee a good integration of those intothe assembly.

As a particular embodiment example, the diodes used are Schottky diodes.These diodes have the advantage of having a very low voltage drop(approximately 0.3 V) limiting the current consumed by the by-pass.

Such a method makes it possible to manufacture flexible and resilientpanels in the form of a matrix of cells. Thus, the panel will be lessimpacted by zones of shades or at the time of a failure of one of thecells. The best tolerance of this panel allow it to obtain performanceincreased during its use on nonplane surfaces. As an example, the panelcan be integrated into a garment or a backpack, it then makes itpossible to store energy for supplying electronics equipments or torecharge batteries. This integration into textiles is not easily toachieve today. Indeed, an existing basic cell on a rigid support has adimension of approximately 16 cm×16 cm. However, thanks to theassembling method as described, it is possible to obtain from a basiccell about 1024 photovoltaic cells having substantially a square with aside of 5 mm. It is then possible to connect these elements in order toform a matrix of thirty-two lines and thirty-two columns. By usingflexible wire elements, it is finally obtained a square with a side ofapproximately 16 cm with a certain flexibility, which is suitable forits integration into a textile.

The assembly obtained can finally be embedded into a flexible adhesiveor encapsulated between two photon transparent layers of flexibleplastic. This makes it possible both to protect the components byensuring a protection against corrosion and water, to keep theflexibility of the assembly, and to avoid the short-circuits betweenwire when the assembly is stressed.

An example of a method for manufacturing a plurality of photovoltaiccells, such as those illustrated in FIGS. 2 to 9, is illustrated inFIGS. 19 to 22. In a first step, a plurality of active zones 16 are madeon an active plate 15. Each active zone 16 comprises at least onephotovoltaic junction made out of a semiconductor material. Such a platecan have the form of a silicon wafer on which a plurality of activezones 16 provided with a photovoltaic junction are made.

Then, a back plate 17 made out of a transparent material, for exampleglass, can be transferred onto the active plate 15 to form an assembly.This back plate 17 comprises cavities 18 arranged so that, for eachactive zone 16 of the active plate 15, a cavity 18 is placed facing oneof the edges of said active zone (FIGS. 19 and 20). In FIG. 20, as theactive zones 16 are arranged in an unordered way, the cavities 18 areconsequently made in the back plate 17.

Lastly, the assembly is cut out along the edges of the various activezones 16 for forming the cells. The cutting path goes through eachcavity to obtain, after cutting, a plurality of cells each comprising atleast one lateral groove (FIG. 21).

Preferably, the active zones form a grid as illustrated in FIG. 22 foroptimizing the number of active zones made on the active plate. Thus,the cavities 18 of the back plate 17 can be made by a plurality ofsubstantially parallel trenches facilitating the cutting of theassembly.

According to an alternative embodiment of the method, the active plate15 is covered with an active layer and the cavities 18 of the back platecan be made by a plurality of substantially parallel trenchesfacilitating the cutting of the assembly. Indeed, the active zone can bea simple PN junction, it is then not necessary to first delimit activezones for each cell.

In order to make photovoltaic cells with two caps, it is possible,before cutting said assembly, to add a second back plate onto the backface of the active plate 15. The back plate on the back face preferablyincludes cavities, or openings, designed to form after cutting theassembly grooves for housing a wire element respectively placed on aside face or the back face of a cell.

According to an manufacture alternative, the active plate 15 can bethinned by its back face in order to make cells with a low thickness. Inthe same way, if the active plate 15 includes a metal layer, the metallayer can be thinned.

Once the back plate 17 is integral with the active plate 15, the activeplate 15 can be thinned so as to let the active zones 16 flush beforethe transfer of another back plate onto the back face of the activeplate 15. In particular, this enables to make a cell such as illustratedin FIG. 6, i.e. with two transparent caps.

Other embodiments of a photovoltaic cell according to the invention aswell as other methods for assembling photovoltaic cells can be imaginedby the man skilled in the art. Thus, although in thepreviously-described examples of cells the covers are placed directly onsemiconductor substrates, it is possible to place the covers ontoanother constitutive layer of the central block. Moreover, one or moregrooves for housing a wire element can be made on any face of thephotovoltaic cell, for example on the front face of the photovoltaiccell through the transparent cover covering the block of the cell.

1-16. (canceled)
 17. Photovoltaic cell comprising: a block including atleast one semiconductor substrate in which is formed at least onephotovoltaic junction connected to a first electrical contact elementwith a first pole and to a second electrical contact element with asecond pole, a first transparent cover arranged on a first face of theblock and delimiting with said block a first groove for housing a firstelectrically conducting wire element.
 18. Photovoltaic cell according toclaim 17, wherein the first groove is a longitudinal groove configuredfor housing the first wire element in a side face of the cell. 19.Photovoltaic cell according to claim 17, wherein a second cover isarranged on a second face of the block, opposite the first face of theblock, the second cover defining with the block a second grooveconfigured for housing a second electrically conducting wire element.20. Photovoltaic cell according to claim 19, wherein the second grooveis a longitudinal groove configured for housing the second wire elementin a side face of the cell.
 21. Photovoltaic cell according to claim 19,wherein the second cover and/or the first cover are placed directly ontothe semiconductor substrate.
 22. Photovoltaic cell according to claim17, wherein at least one of the electrical contact elements connected tothe photovoltaic junction includes a wire element embedded in a groove.23. Photovoltaic cell according to claim 17, wherein one of theelectrical contact elements comprises a metal layer covering thesemiconductor substrate.
 24. Photovoltaic cell according to claim 17,wherein at least one of the electrical contact elements comprises aplurality of conducting arms arranged on a face of the semiconductorsubstrate, said arms being designed to be in contact with or toconnected to a wire element.
 25. Photovoltaic cell according to claim17, comprising a single semiconductor substrate including a photovoltaicjunction.
 26. Photovoltaic cell according to claim 19, wherein thesecond cover being transparent, the block comprises two semiconductorsubstrates including photovoltaic junctions separated by a metal layer,the cell comprising a third longitudinal groove for housing a thirdelectrically conducting wire element designed to be connected to saidmetal layer.
 27. Photovoltaic cell according to claim 19, wherein theblock comprises two semiconductor substrates including photovoltaicjunctions separated by a dielectric, the cell comprising third andfourth grooves respectively formed on a side face at the interfacebetween the dielectric layer and the associated semiconductorsubstrates.
 28. Photovoltaic cell according to claim 27, wherein on bothsides of the dielectric a metal layer is interposed between thedielectric and the associated semiconductor substrate.
 29. Photovoltaiccell according to claim 17, wherein the cells are connected the oneanother by several wire elements, each wire element being embedded inthe grooves of at least two photovoltaic cells.
 30. Method forassembling a plurality of photovoltaic cells according to claim 25,comprising first and second grooves formed on the same side face, themethod comprising the following successive steps: positioning cells inthe form of at least one line so as to form first and second rows ofgrooves, the first groove of a cell being aligned with the second grooveof the adjacent cell, wiring each line of cells, a first electricallyconducting wire being inserted in each groove of the first line ofgrooves, and a second electrically conducting wire being inserted ineach groove of the second line of grooves, alternatively sectioning thefirst and second wire between two adjacent cells, turning over everysecond photovoltaic cell in order to orient all the first covers of thephotovoltaic cells towards the same side.
 31. Method according to claim30, wherein after the step of turning over the cells, each line isstretched, cells of the same line being then arranged alternatively oneither sides of a central axis of the line.
 32. Method for assembling aplurality of photovoltaic cells comprising making of a plurality ofidentical lines of cells according to the method according to claim 30,and in that after the turning-over step, the lines are arranged so as toform a matrix of lines and columns, a third wire being arranged in eachinterval formed between two adjacent columns of the matrix, each thirdwire electrically connecting together the wire elements connecting twoadjacent cells of each line of the matrix.